Hello Paramesh,
On 04/22/2015 12:20 PM, Paramesh Oddepally wrote:
But, in my library(bionic), the same thing is not working afterthe same changes as above(with same main.cc ). Its not printing anything and waiting infinitely. I cannot understand how to interpret this problem, Is it problem with Library?
The run file of my library is similar to the /libc/ run file.
merely compiling the library for Genode is merely the first (and probably the easiest) step of porting a C runtime like Bionic to Genode. The main part of the work is the creation of a libc "back end" that acts as the glue between the C runtime and the underlying Genode system. To give you an idea of the role of this glue, here are two examples:
* The back end has to provide the memory for the C runtime's malloc and free functions. On Linux, the back end of the C runtime performs a mmap system call to obtain chunks of anonymous memory to be used at malloc/free backing store. On Genode, your back end would have to use Genode's RAM session and RM session interfaces instead.
* For input and output (I/O), the back end has to translate I/O function calls (like read, write, stat, etc) to Genode's various session interfaces (terminal session, file-system session, log session, etc). This is far from trivial because, unlike a POSIX system, Genode does not have mechanisms that perfectly correspond to the C runtime function calls. For example, on Genode, there are no file descriptors. So the back end of the C runtime needs to emulate the semantics of file descriptors by using Genode's mechanisms.
To implement a back end for the Bionic C runtime, you may take cues from the back end of our existing libc, which you can find at [1]. But in order to go ahead, you will ultimately need to gain a good understanding of the internal structure of the Bionic library.
I would start with stdout (as you just tried). You first need to determnine the back-end function called by the Bionic library when issuing the printf function, e.g., by following the call graph within the Bionic library. On a Linux system, the back end of the Bionic libc will eventually issue a "write" system call. Your custom back end would instead issue a call to Genode::Log_session::write.
[1] https://github.com/genodelabs/genode/tree/master/repos/libports/src/lib/libc
Good luck! Norman